Patchwork [google,4.7] Generate a label for the split cold function while using -freorder-blocks-and-partition

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Submitter Sriraman Tallam
Date April 19, 2013, 8:43 p.m.
Message ID <CAAs8Hmw4RW0dXPNnRARnnPKjoWkw9yeg3bnXe=04D3dYPVC03Q@mail.gmail.com>
Download mbox | patch
Permalink /patch/238101/
State New
Headers show

Comments

Sriraman Tallam - April 19, 2013, 8:43 p.m.
Hi,

  This patch generates labels for cold function parts that are split when
using the option -freorder-blocks-and-partition.  The cold label name
is generated by suffixing ".cold" to the assembler name of the hot
function.

  This is useful when getting back traces from gdb when the cold function
part does get executed.

I will port this patch to trunk, please let me know what you think.

Thanks
Sri
Patch to generate labels for cold function parts that are split when
using the option -freorder-blocks-and-partition.  The cold label name
is generated by suffixing ".cold" to the assembler name of the hot
function.

This is useful when getting back traces from gdb when the cold function
part does get executed.

Patch

Index: testsuite/gcc.dg/tree-prof/cold_partition_label.c
===================================================================
--- testsuite/gcc.dg/tree-prof/cold_partition_label.c	(revision 0)
+++ testsuite/gcc.dg/tree-prof/cold_partition_label.c	(revision 0)
@@ -0,0 +1,39 @@ 
+/* Test case to check if function foo gets split and the cold function
+   gets a label.  */
+/* { dg-require-effective-target freorder } */
+/* { dg-options "-O2 -freorder-blocks-and-partition --save-temps" } */
+
+#define SIZE 10000
+
+const char *sarr[SIZE];
+const char *buf_hot;
+const char *buf_cold;
+
+__attribute__((noinline))
+void 
+foo (int path)
+{
+  int i;
+  if (path)
+    {
+      for (i = 0; i < SIZE; i++)
+	sarr[i] = buf_hot;
+    }
+  else
+    {
+      for (i = 0; i < SIZE; i++)
+	sarr[i] = buf_cold;
+    }
+}
+
+int
+main (int argc, char *argv[])
+{
+  buf_hot =  "hello";
+  buf_cold = "world";
+  foo (argc);
+  return 0;
+}
+
+/* { dg-final-use { scan-assembler "foo.cold" } } */
+/* { dg-final-use { cleanup-saved-temps } } */
Index: final.c
===================================================================
--- final.c	(revision 198081)
+++ final.c	(working copy)
@@ -1907,6 +1907,9 @@  final_scan_insn (rtx insn, FILE *file, int optimiz
 #endif
   rtx next;
 
+  char *cold_function_name;
+  const char *mangled_function_name;
+
   insn_counter++;
 
   /* Ignore deleted insns.  These can occur when we split insns (due to a
@@ -1934,6 +1937,15 @@  final_scan_insn (rtx insn, FILE *file, int optimiz
 	  targetm.asm_out.function_switched_text_sections (asm_out_file,
 							   current_function_decl,
 							   in_cold_section_p);
+	  /* Emit a label for the split cold section.  */
+	  mangled_function_name
+	    = IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (current_function_decl));
+	  cold_function_name = XNEWVEC (char,
+	      strlen (mangled_function_name) + strlen (".cold") + 1);
+	  sprintf (cold_function_name, "%s%s", mangled_function_name,
+	           ".cold");
+	  ASM_OUTPUT_LABEL (asm_out_file, cold_function_name);
+	  XDELETEVEC (cold_function_name);
 	  break;
 
 	case NOTE_INSN_BASIC_BLOCK: